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1785/1918 includes material issued previously in the annual Bibliography of North America geology, and in cumulative volumes issued by N. H. Darton and F. B. Weeks. 1919/28 cumulation includes material previously issued in the 1919/20-1935/36 issues and also material not published separately for 1927/28. 1929/39 cumulation includes material previously issued in the 1929/30-1935/36 issues and also material for 1937-39 not published separately.